Question: What are the 4 safety classification labels for hydrogen sulfide under the NFPA Fire regulations?
Paraphrase: According to the NFPA Fire regulations, what are the four safety classification labels for hydrogen sulfide?
SPARQL (Wikidata): SELECT ?obj WHERE { wd:Q170591 p:P4952 ?s . ?s ps:P4952 ?obj . ?s pq:P994 ?x filter(contains(?x , '4')) }